1. Field of the Invention
The present invention relates to a method of evaluating positioning accuracy of a magnetic head tester that tests the performance of a magnetic head mounted in a magnetic disc apparatus.
2. Related Art
During the manufacturing process of magnetic heads, tests that write and read signals onto a magnetic medium using the magnetic heads are actually carried out to investigate the performance of the magnetic heads.
FIG. 1 schematically shows the construction of a magnetic head tester. This magnetic head tester includes a magnetic disc driving mechanism 10 such as a spindle motor, a magnetic medium 12 that is rotationally driven by the magnetic disc driving mechanism 10, and a head attaching mechanism 20 that supports a magnetic head 14 that is the tested product. The head attaching mechanism 20 is constructed so that the magnetic head that is the tested product can be interchanged. The head attaching mechanism 20 is supported by a head driving mechanism 22 that drives the magnetic head 14 in the radial direction and the head driving mechanism 22 is supported by a load/unload mechanism 24 that moves the magnetic head 14 towards and away from a surface of the magnetic medium 12.
When a magnetic head is tested using this magnetic head tester, the magnetic head 14 that is the product being tested is attached to the head attaching mechanism 20, the magnetic head 14 is positioned at a predetermined position on the magnetic medium 12 by the head driving mechanism 22 and the load/unload mechanism 24, a signal is written on the magnetic medium 12 by a write control circuit 16, and the signal recorded on the magnetic medium 12 by the magnetic head 14 is then read using a level measuring circuit 18. A control unit 25 carries out an operation of driving the head driving mechanism 22 to feed the magnetic head 14 in pitch increments in the radial direction and detecting the output level of the read signal using the level measuring circuit 18.
However, a write head and a read head provided in the magnetic head 14 are disposed so as to be slightly offset in the track direction (the radial direction of the magnetic medium). The offset amount of the write head and the read head depends on the gap between the write head and the read head formed on a slider, and differs between individual products due to manufacturing fluctuations. Accordingly, the offset amount is measured using a magnetic head tester and magnetic heads are rejected when the offset amount exceeds a tolerance value (see Patent Document 1, for example).
Patent Document 1
Japanese Laid-Open Patent Publication No. H09-288811.